ACTIVE CONTROL EXPERIMENTS FOR ACOUSTIC RADIATION REDUCTION OF A SANDWICH PANEL: FEEDBACK AND FEEDFORWARD INVESTIGATIONS

Experiments were conducted on a square panel of a honeycomb sandwich material, to compare and evaluate various active control strategies for acoustic radiation reduction. The panel was clamped between two soundproofed rooms, the receiving room being equipped with a moving system and a microphone. This paper compares different sensor/actuator arrangements. The two basic configurations are 8 PVDF patches used as sensors on one side of the panel and 8 PZT patches on the other side, versus several accelerometers or microphones as sensors and secondary shakers as actuators. In all cases, the primary excitation is provided by a shaker generating either pure tones or broadband noise on wide frequency bands (0–800 Hz). The second comparison level is relative to the control approaches: LMS feedforward and collocated feedback control strategies are investigated for broadband primary excitations. One of the most interesting aspects of the problem is to evaluate active control methods applied to a highly damped material. In particular, modal analysis and system identification are much more difficult than when applied to lightly damped metallic structures, due to the high modal overlap.